Secondary batteries are widely utilized not only as a substitute for a primary battery but also as a power source for electronic apparatuses such as mobile phones and IT devices. In particular, non-aqueous electrolyte secondary batteries, typically exemplified by a lithium ion secondary battery, have been increasingly applied to electric vehicles and large-scale industrial machines, because of the capability of providing high energy density. Further, to obtain an even higher voltage, non-aqueous electrolyte secondary batteries, which are battery cells, are stacked to constitute a battery module.
In the secondary battery, the electrolyte loaded therein is decomposed and vaporizes because of repeated charge and discharge cycles, and hence the casing is swollen and deformed. In order to suppress such deformation of the casing, many of the battery modules including stacked secondary batteries are provided with binding plates located around the stack so as to tightly hold the stack therebetween, for example as disclosed in Patent Literature 1.
In the case of the lithium ion secondary battery, the charging is performed under a low-current constant-voltage control, and therefore a control circuit is provided for controlling the charging and discharging. In power source units having the battery module in particular, the surface of the plate provided on a side face of the stack is utilized for attaching the control circuit (see FIG. 2 in Patent Literature 1).